Supplemental Petition for Modification of Child Support. Form Number. 12.905(b).Below are some of the Florida Supreme Court approved child support forms in Florida. Here are the rules and processes for a modification to help you successfully modify your child support order in Florida. What Constitutes a 'Substantial Change in Circumstances' in a Child Support Modification Case? Complete the above forms. Have the forms notarized. When Circumstances Change. Case Managers are not authorized to fill out paperwork or to give legal advice. Child Support; Custody; Dissolution of Marriage (divorce); Emergency Pick Up; Name Change; Paternity.